Thanks a lot KazBaker for your prompt reply and for explaining this in much detail. We currently live in Singapore, and have completed our medicals here (3 of us).
I have contacted my child's Early Intervention Program school, and they have suggested either of the following two options.
Go for a full psychological assessment - which will be conducted by a clinical psychologist or an educational psychologist. Psychologist may use ADORS for assessment and will produce a full report to determine the diagnosis.
Visit a doctor to assess his medical condition to chart his developmental milestones. And then, get one of the speech therapists to assess my child for his Speech delay. This is because the panel clinic doctor has suspected a speech delay.
They will also issue a letter from school mentioning his EIP progress, which will detail his progress and his cognitive abilities. We also intend to get another letter from his pre-school to detail how his social interaction is in the school setting. We will probably go ahead with Option 1 and hope for a postive outcome from the assessment.
Our child had amazing progress in the last year, so we hope his diagnosis doesn't point to any adverse conditions. In any case, we have decided to not worry too much about the Visa process/grant but rather focus more on how we could help our child get much better.
Thanks for sharing your personal experience, it's really great to hear about your child's progress. We are quite hopeful that we will see similar progress in my child's speech in the coming months.

Many thanks Quoll. It was a mistake to not do a proper research about the impact of developmental delays/autism on our immigration application. We had no clue about this until we walked into complete our medicals last week, and never thought this would become such an issue. Since we don't use any government support in our current country of residence, we never really thought about this while applying.
We will complete further medical assessments for my child and see how this goes. Thanks for your detailed reply, this is really useful information.

Thanks Quoll. But hypothetically, if these tests concluded my child's case to be eligible for a visa, would they impose any restrictions on seeking educational support in future (i.e. via private schools or speech therapy sessions, if needed).
Also, if the immigration department facilitates these tests and the results are shared with them directly, what additional help would the migration agents usually provide?

Hello,
We have recently submitted our Skilled Independent Visa (subclass 189) application. It was only during our medical examinations we have realised that the development delays/signs of autism in children would be a deal breaker for obtaining a PR visa. My kid (3 years and 4 months) had shown some signs of autism when he was 2.5 years old and has been attending an early intervention program ever since. He also attends a regular play school here in our city.
He was non-verbal just 10 months ago, but his speech has significantly improved in the last few months. He now speaks more than 300-400 words (eg: fruits, vegetables, colours, animals, vehicles, planets, action words, weeks, months etc..) and uses 3-4 word sentences like "I want water please", "open the door", "cover me with a blanket", "I see a phone" etc.. and asks for assistance using sentences like "help me". He can also count numbers up to 50 and trace alphabets among other things. He also started reading 3-letter words without much assistance.
He has been potty trained for over two weeks now and is generally doing well with his needs. We believe he is doing reasonably well in both his schools as we receive positive feedback from his teachers.
As part of his medical examination earlier this week, we have provided the details of his speech delay and his current pre-school program (early intervention) information to the Doctor. Since there was no formal diagnosis of ASD, and considering his recent improvements we didn't mention anything about his earlier signs of autism. Since my kid showed a lack of interest/attentiveness in this session(and also didn't answer couple of questions), the Doctor suggested that he may have to refer his case back to the Australian Immigration department. He basically suggested that the DoHA may ask for additional details from his school about his attention deficit. I now see the following message from Immiaccount.
"A Medical Officer has determined that additional health information is required to determine whether this person meets the health requirement for the visa subclass specified".
Does this mean further medical tests will be conducted? And what tests do they generally conduct to determine my child's condition. I believe they may probably do some psychological evaluation to determine if he is on the spectrum, but not sure how this really works. We have only observed few of these highlighted symptoms in our child recently, and wondering if this would put him on the spectrum and make him ineligible for this Visa.
Please advice if we should seek professional help (George Lombard or Peter Bollard) for this case right away, or wait a bit longer to see the results from further medical tests (if any)? Apologies for the long post, but would really appreciate any valuable inputs from forum members.